1. Field of the Invention
The present invention relates to novel carbapenem (7-oxo-1-azabicyclo[3.2.0]hept-2-en-2-carboxylic acid) compounds, and antibacterial agents containing such compounds as active ingredients, and a process for producing such compounds.
2. Discussion of Background
In recent years, new .beta.-lactam antibiotic substances have been found in nature which have the same .beta.-lactam rings as penicillin derivatives and as cephalosporin derivatives, but which have different basic structures.
For example, naturally derived carbapenem compounds such as thienamycin isolated from the fermentation of Streptomyces cattleya (J. Am. Chem. Soc., vol. 100, p.6491 (1978)), may be mentioned. Thienamycin has an excellent antibacterial spectrum and strong antibacterial activities over a wide range against gram positive bacteria and gram negative bacteria. Therefore, its development as a highly useful .beta.-lactam agent has been expected. However, thienamycin itself is chemically unstable, and it has been reported that it is likely to be decomposed by a certain enzyme in vivo such as renal dehydropeptidase I (hereinafter referred to simply as DHP-I), whereby the antibacterial activities tend to decrease, and the recovery rate in the urine is low (Antimicrob. Agents Chemother., vol. 22, p.62 (1982); ditto, vol. 23, p.300 (1983)).
Merck & Co., Inc. have synthesized many thienamycin analogues with an aim to maintain the excellent antibacterial activities of thienamycin and to secure chemical stability. As a result, imipenem, (5R,6S,8R)-3-[[2-(formimidoylamino)ethyl]thio]-6-(1-hydroxyethyl)-7-oxo-1- azabicyclo[3.2.0]hept-2-en-2-carboxylic acid monohydrate, obtained by formimidation of the amino group of thienamycin, has been practically developed as a pharmaceutical product (J. Med. Chem., vol. 22, p. 1435 (1979)). Imipenem has antibacterial activities of an equal or higher level than thienamycin against various types of bacteria and has .beta.-lactamase resistance. Especially against Pseudomonas aeruginosa, its antibacterial activities are superior to thienamycin by from 2 to 4 times. Further, the stability of imipenem in the solid form or in an aqueous solution is remarkably improved over thienamycin.
However, like thienamycin, imipenem is likely to be decomposed by DHP-I in the human kidney. Therefore, it can not be used for treatment of the urinary-tract infection. Further, it presents toxicity against the kidney due to the decomposition products. Therefore, imipenem can not be administered alone and is required to be used in combination with a DHP-I inhibitor like cilastatin (J. Antimicrob. Chemother., vol. 12 (Suppl. D), p. 1 (1983)). In recent years, imipenem has been frequently used for the treatment and prevention of infectious diseases. Consequently, highly methiciilin resistant Staphylococcus aureus which is resistant to imipenem and imipenem resistant Pseudomonas aeruginosa are increasing in the clinical field. Imipenem does not show adequate treating effects against these resistant bacteria.
As the prior art closest to the present invention, U.S. Pat. No. 4,933,333 may be mentioned. This publication discloses carbapenem compounds having a 2-(aminocarbonyl or N-mono- or N,N-di-lower alkylaminocarbonyl)pyrrolidin-4-ylthio group at the 2-position of the carbapenem structure, represented by meropenem, SM-7338:
(4R,5S,6S,8R,2'S,4'S)-6-(1-hydroxyethyl)-4-methyl-3-[2-(N,N-dimethylaminoca rbonyl)pyrrolidin-4-ylthio]-7-oxo-1-azabicyclo[3.2.0]hept-2-en-2-carboxylic acid, as a typical compound.
.beta.-Lactam antibiotics exhibit selective toxicity against bacteria and show no substantial effects against animal cells. Therefore, they are widely used for treatment of infectious diseases caused by bacteria, as rare antibiotics having little side effects, and thus are highly useful drugs.
However, in recent years, highly methicillin resistant Staphylococcus aureus and resistant Pseudomonas aeruginosa have been isolated frequently from patients with the immunity decreased, as bacteria causing hardly curable infectious diseases. This is regarded as a clinically serious problem. Accordingly, it is strongly desired to develop an antibacterial agent having improved antibacterial activities against such resistant bacteria. Especially with respect to carbapenem compounds, it is desired to improve the antibacterial activities, to improve the stability against DHP-I, to reduce the toxicity against the kidney and to reduce side effects against the central nervous system.
The compounds disclosed in U.S. Pat. No. 4,933,333, particularly meropenem, have the stability against DHP-I substantially improved. However, the antibacterial activities against the above-mentioned highly methicillin resistant Staphylococcus aureus are not adequate, and a carbapenem compound having superior antibacterial activities, is desired.
The present inventors have made extensive researches with an aim to provide novel carbapenem compounds which have excellent antibacterial activities and which are resistant against DHP-I. As a result, they have found that carbapenem compounds of the present invention having, at the 2-position of the carbapenem structure, a group of the formula: ##STR2## wherein R.sup.2 is a lower alkyl group, a lower alkyl group substituted with a hydroxyl group or --COOR.sup.3 (wherein R.sup.3 is a hydrogen atom or a lower alkyl group), A is .dbd.NH, .dbd.NR.sup.4 or .dbd.N(R.sup.4)R.sup.5 (wherein each of R.sup.4 and R.sup.5 which may be the same or different, is a lower alkyl group or a lower alkyl group substituted with a hydroxyl group), p is an integer of from 0 to 3, and each of q and r which may be the same or different, is an integer of from 0 to 5, provided that q and r are not simultaneously 0 and q+r.ltoreq.6, are novel compounds not disclosed in any literatures, and that such compounds have strong antibacterial activities against gram positive bacteria such as Staphylococcus aureus and against gram negative bacteria including Pseudomonas aeruginosa and further exhibit excellent stability against DHP-I. The present invention has been accomplished on the basis of this discovery.